i've got a saltwater fish enthusiast site up and going. it's just running postnuke.

at any rate, i'd like to setup something similar to www.groopz.com but where any user can click any other user on the site and initiate an IM-type session.

been searching entropy chat (although have yet to see a demo), groopz, and things along those lines.

however so far, these tools have been based on an admin watchin who surfs their site and then 'interupts' the user w/ a java IM chat session.

anything out there allowing any pre-defined user to chat w/ any other pre-defined user rather than just an admin having the capabilities?